Hydroconversion multi-metallic catalyst and method for making thereof

ABSTRACT

In a process for forming a bulk hydroprocessing catalyst by sulfiding a catalyst precursor in a co-precipitation reaction, up to 60% of the metal precursor feeds do not react to form catalyst precursor and stay in the supernatant. In one embodiment, at least a precipitant is added to the product mixture at a molar ratio of precipitant to metal residuals in the supernatant ranging from 1.5:1 to 20:1 to precipitate at least 50 mole % of metal ions in the residuals forming additional catalyst precursor. The remaining metal residuals can be recovered via any of chemical precipitation, ion exchange, electro-coagulation, and combinations thereof to generate an effluent stream containing less than 50 mole % of at least one of the metal residuals. In one embodiment, at least one of the metal residuals is recovered and recycled for use as a metal precursor feed in the co-precipitation reaction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Patent Application Ser. No.61/412,768 with a filing date of Nov. 11, 2010. This application claimspriority to and benefits from the foregoing, the disclosures of whichare incorporated herein by reference.

TECHNICAL FIELD

The petroleum industry increasingly turns to heavy crudes, resids, coalsand tar sands, i.e., lower grade hydrocarbon, as sources for feedstocks.The upgrading or refining of these feedstocks is accomplished bytreating the feedstocks with hydrogen in the presence of catalysts toeffect conversion of at least a portion of the feeds to lower molecularweight hydrocarbons, or to effect the removal of unwanted compounds, ortheir conversion to less undesirable compounds

Hydroconversion catalysts can be supported or self-supported(unsupported). Supported catalysts usually comprise of at least oneGroup VIB metal with one or more Group VIII metals as promoters on arefractory support such as alumina. Unsupported (or “bulk”) mixed GroupVIII and Group VIB metal catalysts and catalyst precursors used forhydroconversion processes are known in the art as disclosed in U.S. Pat.Nos. 2,238,851; 5,841,013; 6,156,695; 6,566,296 and 6,860,987.

In the process of making and using hydrotreating catalysts, asubstantial amount of metal residues and wastes are generated in theform of raw and intermediate materials, e.g., in the supernatantgenerated in the recovery of the catalyst precursor precipitate anddischarged in an effluent stream. In some processes for makinghydroconversion catalysts, up to 60% of the metal feed such as Ni, Mo,W, etc., may be wasted and discharged in the effluent stream, puttingpressure on the downstream waste treatment process. As the environmentalimpact of waste disposal such as metal-containing waste materials getsmore scrutinized, there is a need for improved processes to makehydroconversion catalysts with minimal waste. There is also a need foreffective recovery of residual precious metals from reaction effluentsfor re-use in the process of making hydrotreating catalysts.

SUMMARY

In one aspect, the invention relates to an improved method for forming abulk hydroprocessing catalyst with minimal metals in the effluent towaste treatment, the method comprising: co-precipitating at reactionconditions at least one of a Group VIB metal precursor feed and at leasta Promoter metal precursor feed selected from Group VIII, Group IIB,Group IIA, Group IVA and combinations thereof, to form a mixturecomprising a catalyst precursor; isolating the catalyst precursor fromthe mixture, forming a supernatant containing at least a Promoter metalresidual and at least a Group VIB metal residual in an amount of atleast 10 mole % of the metal precursor feeds; treating the supernatantby any of chemical precipitation, ion exchange, electro-coagulation, andcombinations thereof to generate first effluent stream containing lessthan 50 mole % of at least one of the metal residuals; recovering atleast 80 mole % of the metal ions in at least one of the metal residualsto form a metal precursor feed; sulfiding the catalyst precursor formingthe bulk catalyst; and recycling the metal precursor feed to theco-precipitating step.

In one aspect, the invention relates to a process for forming a bulkhydroprocessing catalyst, the method comprises co-precipitating atreaction conditions at least one of a Group VIB metal precursor feed andat least a Promoter metal precursor feed selected from Group VIII, GroupIIB, Group IIA, Group IVA and combinations thereof, to form a mixturecomprising a first catalyst precursor and a first supernatant containinga Promoter metal residual and a Group VIB metal residual in an amount ofat least 10 mole % of the metal precursor feeds; adding at least aprecipitant to the mixture at a molar ratio of added precipitant tometal residuals ranging from 1.5:1 to 20:1 to precipitate at least 50mole % of metal ions in at least one of the metal residuals, forming asecond catalyst precursor; isolating the first and second catalystprecursors forming a second supernatant containing less than 2000 ppm ofmetal ions; and sulfiding the first and second catalyst precursorsforming the bulk catalyst.

In another aspect for an improved method to form a bulk hydroprocessingcatalyst composition, the method comprises: co-precipitating at reactionconditions at least one of a Group VIB metal precursor feed and at leasta Promoter metal precursor feed selected from Group VIII, Group IIB,Group IIA, Group IVA and combinations thereof, to form a mixturecomprising a catalyst precursor; isolating the catalyst precursor fromthe mixture, forming a supernatant containing a Promoter metal residualand a Group VIB metal residual in an amount of at least 10 mole % of themetal precursor feeds; providing at least an exchange resin; contactingthe supernatant with the ion exchange resin for a sufficient amount oftime for at least 50 mole % of metal ions in at least one of the metalresiduals in the supernatant to be exchanged and bound onto the resin,forming a first effluent stream containing unbound metal residuals;eluting the resin to produce an eluate containing the previously boundmetals; recovering at least 80 mole % of metal ions in the unbound metalresiduals in the first effluent stream or at least 80 mole % ofpreviously bound metal ions in the eluate to form at least a metalprecursor feed for use in the co-precipitating step; and sulfiding thecatalyst precursor forming the bulk catalyst.

In another aspect for an improved method to form a bulk hydroprocessingcatalyst composition, the method comprising: co-precipitating atreaction conditions at least one of a Group VIB metal precursor feed andat least a Promoter metal precursor feed selected from Group VIII, GroupIIB, Group IIA, Group IVA and combinations thereof, to form a mixturecomprising a catalyst precursor; isolating the catalyst precursor fromthe mixture, forming a supernatant containing a Promoter metal residualand a Group VIB metal residual in an amount of at least 10 mole % of themetal precursor feeds; supplying the supernatant to a vessel having aplurality of electrodes having a positive or a negative charge providedby a power supply; reacting the electrodes with at least one of themetal precursors, forming a slurry containing insoluble metal compounds;recovering the insoluble metal compounds, forming a first effluentstream containing less than 20 mole % of at least one of the metalresiduals; recovering at least 80 mole % of at least one of the metalresiduals from the first effluent stream to form at least a metalprecursor feed for use in the co-precipitating step, forming a secondeffluent stream contains less than 1000 ppm of one of the metalprecursors; sulfiding the catalyst precursor forming the bulk catalyst;and recycling the metal precursor feed to the co-precipitating step.

In another aspect, the invention relates to an improved method to form abulk hydroprocessing catalyst composition, comprising co-precipitatingat reaction conditions at least one of a Group VIB metal precursor feedand at least a Promoter metal precursor feed selected from Group VIII,Group IIB, Group IIA, Group IVA and combinations thereof, to form amixture comprising a catalyst precursor; isolating the catalystprecursor from the mixture, forming a supernatant containing at least aPromoter metal residual and at least a Group VIB metal residual in anamount of at least 10 mole % of the metal precursor feeds; mixing thesupernatant with at least one of an acid, a sulfide-containing compound,a base, and combinations thereof under mixing conditions at atemperature from ambient to 90° C. for a sufficient amount of time toprecipitate at least 50% of at least one of the metal residuals, whereinthe precipitation is carried out at a pre-select pH; isolating theprecipitate to recover a first effluent containing less than 50 mole %of at least one of the metal residuals in the supernatant; convertingthe precipitate into at least a metal precursor feed; recycling the atleast a metal precursor feed to the co-precipitating step; and sulfidingthe catalyst precursor forming the bulk catalyst.

In another aspect, the invention relates to yet another method to form abulk hydroprocessing catalyst composition, comprising: co-precipitatingat reaction conditions at least a Group VIB metal precursor feed and atleast a Promoter metal precursor feed selected from Group VIII, GroupIIB, Group IIA, Group IVA and combinations thereof, to form a mixturecomprising a catalyst precursor; isolating the catalyst precursor fromthe mixture, forming a supernatant containing at least a Promoter metalresidual and at least a Group VIB metal residual in an amount of atleast 10 mole % of the metal precursor feeds; mixing the supernatantwith at least at least an acid, a sulfide-containing compound, a baseunder mixing conditions at a temperature from ambient to 90° C. toadjust its pH; contacting the supernatant with a chelated ion exchangeresin for a sufficient amount of time for at least 50 mole % of metalions in at least one of the metal residuals in the supernatant to beexchanged and bound onto the resin, forming a first effluent containingless than 1000 ppm of at least one of the metal residuals; eluting theresin to produce an eluate containing the previously resin-bound metals;recovering at least 80 mole % of the unbound metal residuals in thefirst effluent stream or at least 80 mole % of the previouslyresin-bound metals in the eluate to form at least a metal precursorfeed; recycling the metal precursor feed to the co-precipitating step;and sulfiding the catalyst precursor forming the bulk catalyst. In oneembodiment with a weak acid resin, the resin functions as an anionexchange resin with an acidic supernatant for the recovery of Group VIBmetal residuals, and a cation exchange resin with a basic supernatantfor the recovery of Promoter metal residuals.

In yet another aspect, the invention relates to a method for forming ahydroprocessing catalyst composition. The method comprises:co-precipitating at reaction conditions at least a Group VIB metalprecursor feed and at least a Promoter metal precursor feed selectedfrom Group VIII, Group IIB, Group IIA, Group IVA and combinationsthereof, to form a mixture comprising a catalyst precursor; isolatingthe catalyst precursor from the mixture, forming a supernatantcontaining at least a Promoter metal residual and at least a Group VIBmetal residual in an amount of at least 10 mole % of the metal precursorfeeds; mixing the supernatant with at least one of an acid, asulfide-containing compound, and combinations thereof for a sufficientamount of time to precipitate at least a portion of metal ions in atleast one of the metal residuals, wherein the precipitation is carriedout at a first pre-select pH; isolating the precipitate to recover afirst effluent containing less than 50 mole % of metal ions in at leastone of the metal residuals in the supernatant; contacting the firsteffluent with a first chelated ion exchange resin at a second pre-selectpH for a sufficient amount of time for at least 50 mole % of metal ionsin at least one of the metal residuals in the first effluent to be boundonto the resin, forming a second effluent containing less than 1000 ppmof metal ions in at least one of the metal residuals; and contacting thesecond effluent with a second chelated ion exchange resin at a thirdpre-select pH for a sufficient amount of time for at least 50 mole % ofmetal ions in at least one of the metal residuals in the first effluentto be bound onto the resin, forming a third effluent containing lessthan 100 ppm of metal ions in at least one of the metal residuals.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides an overview of an embodiment of a process for making abulk multi-metallic catalyst with minimal loss of metal waste, includingsteps to recover the metal components.

FIG. 2 provides an overview of another embodiment of a process formaking a bulk multi-metallic catalyst including a step to recover metalscomponents with the formation of additional (secondary) catalystprecursor.

FIG. 3 is a block diagram of an embodiment employing electro-coagulationtechnology to recover metal components from the supernatant stream ofFIG. 1.

FIG. 4 is a block diagram of yet another embodiment employingelectro-coagulation technology to recover metal components.

FIG. 5 is a block diagram of an embodiment employing ion-exchangetechnology to recover metal components from the supernatant stream.

FIG. 6 is a block diagram of another embodiment employing ion-exchangetechnology, a combination of anionic and cationic exchangers, to recovermetal components.

FIG. 7 is a block diagram of a third embodiment employing ion-exchangetechnology to recover metal components.

FIG. 8 is a block diagram of an embodiment employing both ion-exchangeand electro-coagulation to recover metal components.

DETAILED DESCRIPTION

The following terms will be used throughout the specification and willhave the following meanings unless otherwise indicated.

SCF/BBL (or scf/bbl, or scfb or SCFB) refers to a unit of standard cubicfoot of gas (N₂, H₂, etc.) per barrel of hydrocarbon feed.

LHSV means liquid hourly space velocity.

The Periodic Table referred to herein is the Table approved by IUPAC andthe U.S. National Bureau of Standards, an example is the Periodic Tableof the Elements by Los Alamos National Laboratory's Chemistry Divisionof October 2001.

“Bulk catalyst” may be used interchangeably with “unsupported catalyst,”or “self-supported catalyst,” meaning that the catalyst composition isNOT of the conventional catalyst form which has a preformed, shapedcatalyst support which is then loaded with metal compounds viaimpregnation or deposition catalyst. In one embodiment, the bulkcatalyst is formed through precipitation. In another embodiment, thebulk catalyst has a binder incorporated into the catalyst composition.In yet another embodiment, the bulk catalyst is formed from metalcompounds and without any binder.

“Precipitant” refers to an additive or compound, which can be in anyform, e.g., liquid or solid form, employed to selectively extractdesired metal or metals from a composition.

“Gel” or “cogel” refers to a solid, gelatinous material that is formedin the precipitation, co-precipitation, or cogelation reaction betweenat least two metal precursor feeds.

“Co-precipitate” or co-precipitating refers to the reaction between atleast two metal precursor feeds to form a catalyst precursor in the formof a gel or cogel.

“Metal precursor feed” means a reactant feed to the co-precipitationreaction to form a catalyst precursor, which reactant feed can be asolid, a liquid, or partially solid, and which reactant feed can beeither mono-metallic or multi-metallic.

“Metal residual” in either plural or singular form, referring toresidual metal compound(s) left in solution from the co-precipitationreaction of the metal precursor feed.

“Supernatant” (or “supernatant stream”) refers to the remainder liquidafter the isolation of the catalyst precursor, which liquid containsmetal residuals, e.g., the residual metal compound(s) left in solutionfrom the reaction to form catalyst precursors. In one embodiment, thesupernatant contains metal residuals in an amount of up to 60 molepercent (mole %) of the metal ions of the metal precursor feed.

“Secondary catalyst precursor” (or “additional catalyst precursor”)refers to the additional catalyst precursor formed with residual metalcompounds (e.g., metal residuals) in the supernatant.

“Bound metal ions” refers to metals ions that are exchanged and boundonto ion-exchange resin.

“Unbound metal residuals” refers to the metal residuals that do notreact and are not bound onto the ion-exchange resin.

“Effluent” (or “effluent stream”) refers to the waste water streamdischarged from a metal recovery step. In one embodiment, the effluentis sent to waste water treatment.

“Treating” in the context of treating an effluent stream or an eluaterefers to a step wherein the stream is processed in a way thatprecipitate is formed, e.g., via chemical precipitation,electro-coagulation, evaporation, etc., or combinations thereof. Thetreating step may comprise an isolation step to recover a precipitateand a solution.

“ppm” of a metal in the supernatant or effluent stream refers to partsper million of the metal ions in the stream.

% of a metal (expressed as concentration of the metal in a compositionor a stream) refers to its mole %, unless indicated otherwise.

“One or more of” or “at least one of” when used to preface severalelements or classes of elements such as X, Y and Z or X₁-X_(n), Y₁-Y_(n)and Z₁-Z_(n), is intended to refer to a single element selected from Xor Y or Z, a combination of elements selected from the same common class(such as X₁ and X₂), as well as a combination of elements selected fromdifferent classes (such as X₁, Y₂ and Zn).

“Hydroconversion” or “hydroprocessing” is meant any process that iscarried out in the presence of hydrogen, including, but not limited to,methanation, water gas shift reactions, hydrogenation, hydrotreating,hydrodesulphurization, hydrodenitrogenation, hydrodemetallation,hydrodearomatization, hydroisomerization, hydrodewaxing andhydrocracking including selective hydrocracking. Depending on the typeof hydroprocessing and the reaction conditions, the products ofhydroprocessing can show improved viscosities, viscosity indices,saturates content, low temperature properties, volatilities anddepolarization, etc.

700° F.+ conversion rate refers to the conversion of a feedstock havinga boiling point of greater than 700° F.+ to less than 700° F. (371° C.)boiling point materials in a hydroconversion process, computed as(100%*(wt. % boiling above 700° F. materials in feed−wt. % boiling above700° F. materials in products)/wt. % boiling above 700° F. materials infeed)).

“Shaped catalyst precursor” means a catalyst precursor formed (orshaped) by spray drying, pelleting, pilling, granulating, beading,tablet pressing, bricketting, using compression method via extrusion, orother means known in the art, or by the agglomeration of wet mixtures.The shaped catalyst precursor can be in any form or shape, including butnot limited to pellets, cylinders, straight or rifled (twisted)trilobes, multiholed cylinders, tablets, rings, cubes, honeycombs,stars, tri-lobes, quadra-lobes, pills, granules, etc.

“Promoter Metal” (or “promoter metal”) may be used interchangeably withM^(P), referring to a material that enhances the activity of a catalyst(as compared to a catalyst without the Promoter Metal, e.g., a catalystwith just a Group VIB metal).

In the sections that follow, the reference to “molybdenum” and/or“tungsten” is by way of exemplification only for the Group VIB metal tobe recovered in the supernatant, and is not intended to exclude otherGroup VIB metals/compounds and mixtures of Group VIB metal/compounds forrecovery. Similarly, the reference to “nickel” is by way ofexemplification only for the Promoter metal component(s) for recovery,and is not meant to exclude other Group VIII, Group IIB, Group IIA,Group IVA metals and combinations thereof that can be in the supernatantfor subsequent recovery.

The catalyst precursor can be a hydroxide or oxide material, preparedfrom at least a Promoter metal precursor feed and at least a Group VIBmetal precursor feed. The bulk or unsupported catalyst precursor madecan be converted into a hydroconversion bulk catalyst (becomingcatalytically active) upon sulfidation. The bulk catalyst is for use inhydrodesulfurization (HDS), hydrodearomatization (HDA), andhydrodenitrification (HDN) processes. Further details regarding thedescription of the catalyst precursor and the bulk catalyst formedthereof are described in a number of patent applications and patents,including U.S. Pat. Nos. 7,544,285, 7,615,196, 6,635,599, 6,635,599,6,652,738, 7,229,548, 7,288,182, 6,566,296, 6,860,987, 6,156,695,6,162,350, 6,299,760, 6,620,313, 6,758,963, 6,783,663, 7,232,515,7,179,366, 6,274,530; US Patent Publication Nos. US20090112011A1,US20090112010A1, US20090111686A1, US20090111685A1, US20090111683A1,US20090111682A1, US20090107889A1, US20090107886A1, US20090107883A1,US2007090024; U.S. patent application Ser. No. 12/432,719, U.S. patentapplication Ser. No. 12/432,721, U.S. patent application Ser. No.12/432,723, U.S. patent application Ser. No. 12/432,727, U.S. patentapplication Ser. No. 12/432,728, and U.S. patent application Ser. No.12/432,728, the relevant disclosures with respect to the catalystprecursor and catalyst composition are included herein by reference.

In one embodiment, the catalyst precursor is a bulk multi-metallicoxide, comprising of at least one Group VIII non-noble material and atleast two Group VIB metals. In one embodiment, the ratio of Group VIBmetal to Group VIII non-noble metal in the precursor ranges from about10:1 to about 1:10. In another embodiment, the oxide catalyst precursoris of the general formula: (X)_(b)(Mo)_(c)(W)_(d)O_(z); wherein X is Nior Co, the molar ratio of b:(c+d) is 0.5/1 to 3/1, the molar ratio ofc:d is >0.01/1, and z=[2b+6 (c+d)]/2. In yet another embodiment, theoxide catalyst precursor further comprises one or more ligating agentsL. The term “ligand” may be used interchangeably with “ligating agent,”“chelating agent” or “complexing agent” (or chelator, or chelant),referring to an additive that combines with metal ions, e.g., Group VIBand/or Promoter metals, forming a larger complex, e.g., a catalystprecursor.

In another embodiment, the catalyst precursor is in the form of ahydroxide compound, comprising of at least one Group VIII non-noblematerial and at least two Group VIB metals. In one embodiment, thehydroxide catalyst precursor is of the general formulaA_(v)[(M^(P))(OH)_(x)(L)^(n) _(y)]_(z)(M^(VIB)O₄), wherein A is one ormore monovalent cationic species, M refers to at least a metal in theirelemental or compound form, and L refers to one or more ligating agent.In one embodiment, A is at least one of an alkali metal cation, anammonium, an organic ammonium and a phosphonium cation. In oneembodiment, A is selected from monovalent cations such as NH4+, otherquaternary ammonium ions, organic phosphonium cations, alkali metalcations, and combinations thereof.

In one embodiment, the optional ligating agent L has a neutral ornegative charge n<=0. The term “charge-neutral” refers to the fact thatthe catalyst precursor carries no net positive or negative charge.Examples of ligating agents L include but are not limited tocarboxylates, carboxylic acids, aldehydes, ketones, the enolate forms ofaldehydes, the enolate forms of ketones, and hemiacetals; organic acidaddition salts such as formic acid, acetic acid, propionic acid, maleicacid, malic acid, cluconic acid, fumaric acid, succinic acid, tartaricacid, citric acid, oxalic acid, glyoxylic acid, aspartic acid, alkanesulfonic acids such as methane sulfonic acid and ethane sulfonic acid,aryl sulfonic acids such as benzene sulfonic acid and p-toluene sulfonicacid and arylcarboxylic acids; carboxylate containing compounds such asmaleate, formate, acetate, propionate, butyrate, pentanoate, hexanoate,dicarboxylate, and combinations thereof.

In one embodiment, M^(VIB) is at least a Group VIB metal having anoxidation state of +6. In another embodiment, M^(VIB) is a mixture of atleast two Group VIB metals, e.g., molybdenum and chromium. M^(VIB) canbe in solution or in partly in the solid state

In one embodiment, M^(P) is at least a promoter metal. In oneembodiment, M^(P) has an oxidation state of either +2 or +4. M^(P) isselected from Group VIII, Group IIB, Group IIA, Group IVA andcombinations thereof. In one embodiment, M^(P) is at least a Group VIIImetal with M^(P) having an oxidation state P of +2. In anotherembodiment, M^(P) is selected from Group IIB, Group IVA and combinationsthereof. In one embodiment, M^(P) is selected from the group of IIB andVIA metals such as zinc, cadmium, mercury, germanium, tin or lead, andcombinations thereof, in their elemental, compound, or ionic form. Inanother embodiment, M^(P) is a Group IIA metal compound, selected fromthe group of magnesium, calcium, strontium and barium compounds. M^(P)can be in solution or in partly in the solid state, e.g., awater-insoluble compound such as a carbonate, hydroxide, fumarate,phosphate, phosphite, sulphide, molybdate, tungstate, oxide, or mixturesthereof.

Embodiments of the process for making the unsupported or bulk catalystprecursor are as described in the references indicated above, andincorporated herein by reference. In one embodiment, the first step is amixing step wherein at least one Group IVB metal precursor feed and atleast one Promoter metal precursor feed are combined together in aprecipitation step (also called cogelation or co-precipitation), whereina catalyst precursor is formed as a gel. The precipitation (or“cogelation”) is carried out at a temperature and pH under which thepromoter metal compound and the Group VIB metal compound precipitate(e.g., forming a gel). In one embodiment, the temperature is between25-350° C. and at a pressure between 0 to 3000 psig. The pH of thereaction mixture can be changed to increase or decrease the rate ofprecipitation (cogelation), depending on the desired characteristics ofthe catalyst precursor product. In one embodiment, the mixture is leftat its natural pH during the reaction step(s). In another embodiment,the pH is maintained in the range of 0-12.

In one embodiment, at least one chelating (ligating) agent and/or othermaterials including but not limited to diluents (or binders) can beadded to the precipitation step in the formation of the catalystprecursor. The additive can be added concurrently with the metalprecursor feedstock, or after the formation of the catalyst precursorgel.

After the co-precipitation step, the catalyst precursor is isolated orrecovered in a liquid removal step using known separation processes suchas filtering, decanting, centrifuging, etc. The remainder liquid, i.e.,the supernatant, in one embodiment contains metal residuals in an amountof at least 10 mole % and up to 60 mole % of the metal ions in the metalprecursor feeds, as elemental metals or metal compounds, referringgenerally as “metals.” In another embodiment, the supernatant containsmetal residuals in an amount from 15 to 40 mole % of the metal ions inthe metal precursor feeds. In one embodiment for making a Ni—Mo—Wcatalyst, the supernatant contains from 5000 to 10000 ppm Mo, 1000 to5000 W, and 500 to 3000 ppm Ni.

After the isolation of the catalyst precursor, metals in the supernatantin one embodiment can be recovered using any of chemical precipitation,electro-coagulation, ion-exchange, evaporation, membrane filtration, andcombinations thereof. In another embodiment, the metal recovery step canalso carried out with the addition of at least a precipitant to form asecondary catalyst precursor. The metal recovery can be done in batchmode, continuous mode, or combinations thereof.

Description of the various metal recovery process steps forrecycling/incorporation into the catalyst precursor follows. Any of thesteps can be employed by itself or in combination with other steps,reducing metals in the effluent stream to waste treatment to less than5000 ppm in one embodiment, less than 1000 ppm in a second embodiment,less than 500 ppm in a third embodiment, and less than 50 ppm in afourth embodiment.

Chemical Precipitation: In one embodiment, the supernatant is treated toadjust the pH at a level at which selective precipitation of at least aportion of the metal ions in at least one of the metal residuals occurs(“pre-selected pH”). In one embodiment, at least a portion means atleast 25 mole %, and at least 50% in a second embodiment. Up to 99% ofmetal ions in at least one of the metal residuals can be recovered insubsequent precipitation steps to precipitate any metal compoundsremaining in solution. The optimal pH for precipitation depends on themetal(s) to be recovered and the counter ion used in the precipitatingagent (e.g., hydroxide, carbonate, sulfide, etc.). In one example withthe supernatant containing both Ni and Cr metal residuals, the pH may bepre-selected to precipitate both metals.

In one embodiment, at least an acid is employed to adjust the pH of thesupernatant to the pre-select pH. The acid used to precipitate thesupernatant may include any acid with a relatively high ionizationconstant. In one embodiment, the acid is used in a strength ranging from1.0 to 12.0 normal. In one embodiment, the acid is selected from thegroup of sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid,acetic acid, oxalic acid, nitric acid, and mixtures thereof.

In one embodiment, the supernatant is treated with at least aprecipitating agent to extract out at least one of metals as aprecipitate. The selection of the precipitating agent(s) depends on anumber of factors, including but not limited to the metal(s) to berecovered as a precipitate. The agents can be added all at once or insequence. The chemical precipitation can be carried out in batch orcontinuous mode.

In one embodiment with a Group VIB metal such as molybdenum, chromium,etc., as one of the metals to be recovered, the precipitating agent isselected from the group of calcium hydroxide, sodium hydroxide andmagnesium oxide, with MgO is preferred. In another embodiment, theprecipitating agent is a mixture of sodium carbonate and hydrogenperoxide.

In one embodiment, the pH of the supernatant is adjusted such that atleast 95% of the Group VIB metals precipitate. In another embodiment,the pre-selected pH is set at less than 3.5 to precipitate at least 90%of the soluble molybdenum metal compounds. In another embodiment withtungsten as a co-catalyst, the pre-selected pH is from 1 to 2 toinitiate precipitation of at least 95% of soluble metal compounds. Inyet another embodiment, nitric acid is added to the supernatant for a pHof 1 to 2 to precipitate out Mo and W as H₂MoO₄ and H₂WO₄ respectively,removing at least 75% of the unreacted Group VIB precursors fromsolution. Generally, several metals can form a precipitate at a givenpH. For example, at a pH level of less than 3, both Mo and Ni (and Co,if any) precipitate although more molybdenum precipitates relative tonickel. Additionally, the precipitating concept described herein can berepeated at another pre-selected pH or pH range to precipitate othermetals.

In one embodiment, the precipitating agent is a sulfide-containingcompound, e.g., a water soluble sulfide, a water soluble polysulfide, ormixtures thereof, employed to adjust the pH of the supernatant to alevel at which precipitation of metals occurs. In one embodiment,hydrogen sulfide, a combination of hydrogen sulfide and caustic soda,ammonium sulfide, NaHS, or Na₂S, or mixtures thereof can be used in anamount of about 0.05 to 0.2 molar to precipitate out molybdenum,tungsten, and the like.

Depending on the metal residuals present in the supernatant and theprecipitation agent used, in one embodiment, chemical precipitation iscarried out in one single step. In another embodiment, chemicalprecipitation is carried out as a multi-step process. The multi-processcan be a combination of basic and acid precipitation steps, with eitherthe basic precipitation or acid precipitation step to be the first step.

In one embodiment of the acid precipitation step, an acid is added tothe supernatant to adjust the pH and precipitate out most of the metalsas metal compounds such as molybdate, tungstate, etc., in a slurrymixture. The metal precipitates are isolated from the slurry usingseparation means known in the art, resulting in a filtrate streamcontaining less than 25% of the metal ions in the metal residualsoriginally in the supernatant. In the basic precipitation step, analkaline earth metal compound, e.g., alkaline halides, particularlycalcium halide, can be added to the filtrate to further extract outmetals. The precipitate is recovered in a separator to separate outmetals such as CaMoW₄, CaWO₄, and the like to waste disposal. Theeffluent containing less than 100 ppm metals can be sent to the sewer.

In one embodiment, the chemical precipitation (acid or basic) of themetal complexes is carried out under mixing conditions at a temperaturein the range of 50 to 95° C., and for a sufficient amount of time, e.g.,for at least 1 hour, for at least 75% of the Group VIB and group VIIImetals to precipitate out. In one embodiment, the precipitation iscarried out at a temperature of 70° C. and a pH level between 1.2 to2.5. In another embodiment, the pH is adjusted to a level between 1 to4. In one embodiment, the pH is continuously regulated for at least partof the precipitation step with continuous addition of additives, e.g.,an acid, calcium oxide, potassium hydroxide solution, sulfide-containingcompound, etc., to control the precipitation rate as well as the type ofmetal complexes to precipitate. In one embodiment, a sufficient amountof sulfuric acid (20-100% by weight) is used to adjust the pH to thedesired target level, with the mixture being maintained at a temperatureof 60-90° C. for 1 to 3 hours, until at least 75% of the Group VIBmetals precipitate out. pH controllers known in the art can be used toautomatically measure and control the pH, maximizing the amount ofmetals precipitated. A voltametric sensor can be used to control the pH.

After precipitation, the solid precipitate containing metal complexescan be separated or isolated from the effluent by known means includingbut not limited to settling, filtration, decantation, centrifugation,magnetic separation, dissolved air flotation, vortex separation,inclined plate separation, etc., or combinations thereof. In oneembodiment, the solid precipitate comprises primarily of Group VIB metalcomplexes, e.g., molybdate, chromate, tungstate, and the like. In oneembodiment, a basic solution, e.g., ammonium chloride, ammonium citrate,ammonium lactate, potassium hydroxide, potassium formate, sodiumhydroxide, sodium acetate, or ammonium hydroxide solution is added todissolve the precipitate, producing a saturated solution having a pH ofabout 5 to about 7. The solution may be cooled from its saturationtemperature to room temperature wherein ammonium polymolybdate (e.g.,ammonium heptamolybdate or AHM) and ammonium polytungstate (e.g.,ammonium heptatungstate or AHT) precipitate out. The solution can berouted or recycled to the co-precipitation reaction as metal precursorfeed.

In one embodiment for a process to make a multi-metallic catalystcontaining a Group VIB metal such as molybdenum or chromium, thesupernatant may be reduced with carbon monoxide or low molecular weightoxygenated hydrocarbons in a redox reaction. The reduction results inthe precipitation of a Group VIB oxide product, e.g., a hydratedchromium oxide, and a spent liquor containing alkali metal salts ofcarbonate or bicarbonate, which is dehydrated to yield alkali metalsalts and wastewater effluent containing less than 50 ppm Group VIBmetals to sewer.

Electro-coagulation: In one embodiment, electro-coagulation running ineither batch or continuous mode, is employed to recover metals from thesupernatant using sacrificial electrodes. The electrodes may befabricated from materials which may sacrifice or donate ions in anelectrolytic process, e.g., iron, titanium, platinum, steel, aluminium,copper carbon, metal-impregnated plastics, ceramics or the like. In oneembodiment, iron is used in the cathodes. In another embodiment,aluminium is used in the cathodes, forming insoluble complexes withvarious Promoter metal residuals in the supernatant, for a removal ofPromoter metals such as Ni, Zn, Co, etc. of at least 75 mole % in oneembodiment and 90 mole % in a second embodiment. In one embodiment,three dimensional electrodes are used for increased effective areainstead of two-dimensional plates as electrodes. In another embodiment,the electrodes comprise substantially parallel metallic electrolyticplates.

In the reactor vessel, supernatant meanders through the electrodes andis under the influence of the electromotive force from the electricalcurrent supplied to the electrodes. In one embodiment, power is avoltage source that supplies at least 150 amperes at a minimum of 15volts. Power supply can be either direct current or alternating current.The removal of metals from the supernatant as metal complexes can beoptimized by varying a number of factors, e.g., the amperage, voltage,current density, flow rate of the supernatant, the pH of thesupernatant, run time, etc. In one embodiment, the electro-coagulationprocess is carried out for 15 minutes to 5 hours. In a secondembodiment, for ½ to 3 hours. In a third embodiment, 60 to 90 minutes.In another embodiment, the electro-coagulation is carried out inconjunction with ultrasound and agitation to aid with the metal removal.

Depending on the selection of the electrodes, at least 75% of at leastone of the metal ions in the metal residuals, e.g., Promoter metalresiduals or the Group VIB metal residuals, are removed as metalcomplexes. In one embodiment, at least 90% of metal ions in the Promotermetal residuals are removed as insoluble compounds, with essentially allof (e.g., at least 95%) the metal ions in the Group VIB metal residualsstill remaining in solution. In another embodiment, at least 90% of themetal ions in the Group VIB metal residuals are removed from thesupernatant as precipitates with essentially all of the Promoter metalresiduals still remaining in solution.

In one embodiment with the use of aluminium is used as electrodes,Promoter metals in the supernatant, e.g., group VIII compounds, comeinto contact and react via oxidation/reduction with the dissolvedmetallic ions subsequently form a slurry containing in-solubleby-products such as NiAlO₄. The pH of the slurry ranges from 6 to 10 inone embodiment, and 4 to 7 in a second embodiment. The insoluble byproducts can be isolated and recovered by known means includingsettling, filtration, decantation, centrifugation, etc., or combinationsthereof, yielding an effluent stream substantially free of insolubleby-products, e.g., less than 50 ppm of Promoter metals such as Ni. Afterrecovery, the insoluble by-products containing recovered metals, e.g.,NiAlO₄, can be sent to waste disposal.

In one embodiment, prior to the electro-coagulation vessel, chemicalprecipitation method is employed with the pH of the supernatant beingcontrolled or adjusted to a certain pre-selected level with the additionof basic or acid chemical agents. In one embodiment, the pH of thesupernatant is adjusted to between 5-9. In another embodiment, the pH isadjusted to about 7. In yet another embodiment, an oxidizing agent isadded to the supernatant prior to the reaction in theelectro-coagulation vessel, with the oxidizing agent selected from thegroup of oxygen, chlorine, permanganate, hydrogen peroxide and ozone.The oxidizing agent helps enhance oxidation/reduction reaction toprecipitate out the metals.

In one embodiment, the effluent stream from the electro-coagulation stepcan be further treated by a chemical precipitation step with theaddition of a sufficient amount of an acid and the like, in an acidprecipitator, under mixing conditions to adjust the pH to a pre-selectedpH, e.g., 3 or less, precipitating out Group VIB metals as molybdate,tungstate, and the like. In one embodiment, the precipitate isre-dissolved in an aqueous ammonium hydroxide solution, which isfiltered and subsequently crystallized to produce a high purity ammoniummolybdate/ammonium tungstate product. These products can be subsequentlyrecovered and use as metal precursor feeds. The effluent from thischemical precipitation step in one embodiment contains less than 2000ppm Mo, less than 500 ppm W, and minimal amounts of Promoter metalresiduals, e.g., less than 50 ppm Ni.

In yet another embodiment, the effluent stream from the chemicalprecipitation step is further treated with a calcium compound, e.g.,CaSO₄, CaCO₃, etc., for the recovery of any residual Group VIB metals ascalcium salts for waste disposal, and for an effluent stream from theprocess with less than 10 ppm of either Group VIB metals or Promotermetals. In one embodiment, the amount of calcium added is at leaststoichiometric to convert the Group VIB values to CaMoO₄, CaWO₄, and thelike. In another embodiment, the ratio ranges from 2/1 to 50/1. In oneembodiment, the calcium treatment is at a temperature ranging from 75°C. up to the boiling point of the solution employed, for 5 minutes toseveral hours.

Depending on the metal residuals in the stream to be treated and theelectrodes used, the effluent stream from the electro-coagulation stepin one embodiment contains less than 1000 ppm metals. In a secondembodiment, less than 500 ppm metals. In a third embodiment, less than100 ppm metals. In a fifth embodiment, less than 50 ppm metals.

Ion-Exchange: The recovery of metals from the supernatant can also becarried out via ion-exchange. The metal recovery rate depends on anumber of factors, including but not limited to the types of resins usedin the ion-exchange bed, the concentration of the metals in thesupernatant, the pH of the supernatant, as well as the flow velocity ofthe supernatant through the ion-exchange resin.

Depending on the metals to be recovered/removed from the supernatant,either anion exchange and/or cation exchange technology may be employedto exchange ions such as hydrogen and hydroxyl ions on the resin for atleast 50% of the metal ions from at least one of the metal residuals inthe supernatant. The metal ions are “exchanged” and bound onto theresin. In another embodiment, at least 80% of the metal ions of at leastone of the metal residuals are exchanged with ions in the resin andbound onto the resin. The unbound metal residuals remain in the effluentstream for subsequent metal recovery and/or water treatment if desired.

In one embodiment, both anion and cation exchange columns are used forthe recovery. In one embodiment, the anion and cation exchange columnsemploy the same type of ion-exchange resin, with the pH of thesupernatant in each column being adjusted to control the metalscavenging affinity of the resin, and for the column to function as ananion or a cation exchange column.

Depending on the metals to be recovered from the supernatant and theresins to be used, the ion-exchange can be carried out at a temperatureranging from ambient to 90° C. in one embodiment, and 50 to 80° C. inanother embodiment. The contact time varies depending on a number offactors, in one embodiment ranges from 1 to 60 bed volumes per hour. Inanother embodiment, from 2 to 20 bed volumes per hour. In a thirdembodiment, from 3 to 10 bed volumes per hour.

In one embodiment, a short bed column is used for the metal recovery. Inanother embodiment, either a single column or a series of columns or bedcan be employed. The metals accumulate to a high level on the first bedand the second bed is used to remove the residual metals to the desiredtarget. Either single pass or dual pass ion-exchange system may beemployed. The columns may be operated in batch, continuous, orsemi-batch mode. In one embodiment, metal recovery is operatedcontinuously with an inlet for the supernatant stream and an outlet fordischarging the treated stream. In one some embodiments after a run, theresins may be regenerated by rinsing with a suitable acid, or an aqueoussolution of suitable hydroxide. In one embodiment, the supernatant isfirst heated to a temperature between 50-80° C. degree to improve thekinetics to the exchange process.

The ion-exchange media comprises an ion exchange resin or a mixture ofion exchange resins. Suitable ion exchange resins may be selected fromthe group consisting of strong base anion exchange resins, weak baseanion exchange resins, strong acid cation exchange resins, weak acidcation exchange resins, chelating resins, and mixtures thereof. In oneembodiment, the ion exchange resins have an average particle size offrom 150-2000 μm. In another embodiment, the ion exchange resin has anaverage particle size of from 300-1200 μm. The average particle size ofthe ion exchange resin may be measured by various analytical methodsgenerally known in the art including, for example, ASTM E-11-61.

In one embodiment, cation resins are employed to exchange hydrogen ionsfor positively charged ions such as Promoter metals, e.g., copper,nickel, etc. In another embodiment, anion resins may be employed toexchange hydroxyl ions for negatively charged ions such the Group VIBmetals, e.g., chromates, molybdate, tungstate, etc. In yet anotherembodiment, anion technology employing cation ion chelated resins toremove anions such as Group VIB metals from the supernatant. In oneembodiment of anion exchange, the resin is of the weakly basic type. Inone embodiment, the anion exchange resins comprise an intermediate amineas the exchange site. In another embodiment, the resin used is a mixtureof secondary and tertiary amines. In a third embodiment, the resin is apolystyrene divinyl benzene. Other examples of anion exchange resinsinclude but are not limited to tertiaryamine in styrene divinyl benzenematrices, tertiary amine type resins, epichlorhydrine-polyaminecondensation-type (aliphatic polyamine types) type resins as well asequivalent types, which are effective to selectively adsorb themolybdate anions/tungstate anions in a substantially neutral medium. Inone embodiment, the resin is a polyampholite (chelating ion-exchange).Chelating polymeric resin comprises copolymers with covalently-linkedfunctional groups, containing one or more donor atoms (Lewis Base), forforming coordinated bindings with most metal ions. In one embodiment, achelating exchange resin with amine functionality is employed. Inanother embodiment, a chelating exchange resin with selectivity fortransition metal cations over alkali or alkaline earth cations isemployed. In yet another embodiment, the chelating exchange resin has atleast one substituent selected from hydroxy, ether, amine, quaternaryamine, a divalent sulfur substituent, amine oxide and hydroxy amineExamples of commercially available chelating exchange resins include butare not limited to DOWEX™ G-26 resin, DOWEX™ MAC-3 resin, DOWEX™ M4195resin, Amberlite™ IRC86 resin, and Amberlite™ IRC748 resin.

In one embodiment with the use of a weak acid chelating resin, the resinacts as an anion exchange resin in an acidic pH range below its point ofzero charge, and a cation exchange resin above its point of zero charge,at a neutral to basic pH. In one embodiment, the supernatant pH isadjusted to a basic range, e.g., 6-7 prior to contact with the resin. Inone embodiment with the use of a chelating exchange resin, depending onthe adjusted pH of the supernatant and the selection of the resin, theresin may function as an anion or a cation exchange resin. In oneembodiment, the resin acts as an anion exchange resin with an acidic pH,e.g., in the range of 1 to 3, and a cation exchange resin with a neutralor basic pH in the range of 6-8. In one embodiment, the supernatant pHis adjusted to a level from 1 to 1.5 prior to treatment for the removalof Group VIB metal ions such as molybdate in an exchange columnfunctioning as an anion exchange column. The effluent from the anionexchange column is adjusted to a pH of 6 to 7 in the next column inseries, wherein the same chelating exchange resin with the change in thepH functions as a cation exchange resin for the removal of a Group VIIImetal ion such as Ni²⁺. The effluent stream from the second exchangecolumn (to waste treatment) contains less than 50 ppm of Group VIB andPromoter metals in one embodiment, and less than 10 ppm in a secondembodiment.

In one embodiment, a cation resin is first pre-conditioned with a diluteacid, e.g., sulfuric acid to effect conversion thereof to the hydrogenform. In another embodiment, an anion resin is first conditioned with ahydroxide to facilitate the absorption of metal ions.

After loading, metal ions previously bound onto the resin can bestripped by eluting the resin with an acid, e.g., nitric acid, sulphuricacid, etc., at concentrations of about 5 to about 10% acid in oneembodiment. In one embodiment, the resin is eluted with an eluantcomprising but not limited to a carbonate/bicarbonate, e.g., 0.05-0.5molar ammonium carbonate to elute any Group VIB metals thereof. In athird embodiment, a weak base anion resin is eluted with sodiumhydroxide to regenerate the resin. The elution is for a sufficient oftime, e.g., at least 15 minutes, and at a sufficient temperature toremove at least 95% of the previously resin-bound ions to regenerate theresin.

In one embodiment, the amount of acid used as eluant is sufficient toprovide a pregnant solution (eluate) containing 5 to 25 gpl of Promotersalts such as nickel chloride, nickel sulphate, nickel nitrate, etc.,depending on the acid used. In one embodiment, the pregnant solutioncontaining Promoter metal salts, e.g., Ni(NO₃)₂ is routed back to thecogelation step as metal precursor feed. The treated process stream inone embodiment is routed to a chemical precipitation step for recoveryof the Group VIB metals as precursor feeds for use in theco-precipitation step.

In one embodiment, cation chelated resins are employed for theremoval/recovery of Group VIB metals via anion exchange. The eluate issubsequently treated by chemical precipitation to remove Group VIIIPromoter metals. In another embodiment, cationic exchange is used tofirst extract Promoter metals, e.g., group VIII, group IIB metals suchas nickel from the supernatant. In the cation-exchanger, a resin isselected to selectively exchange Promoter metals such as nickel, cobalt,and the like from an incoming level of >1000 ppm to less than 50 ppm inthe effluent stream. In another embodiment, Promoter metals in theeffluent stream are reduced to a level of less than 20 ppm. In oneembodiment, at least 90% of the Promoter metals are removed. In a secondembodiment, at least 95%. In a third embodiment, the effluent streamfrom the ion-exchange column contains less than 10 ppm of Promotermetals such as Ni. The type of resin used in the cation-exchange columnsdepends on the concentration and type of Promoter metal(s) to be removedfrom the supernatant. In one embodiment, the resin containsbis-picolylamine.

In one embodiment with the use of anionic exchange, at least 20 to 99%of the Group VIB metals in the process stream may be removed by theadsorption media. In another embodiment, from 60 to 85% of Group VIBmetals may be removed by the resins.

Successive Filtration: In one embodiment, filtration is employed inaddition to or in place of any of the metal recovery steps describedabove. The supernatant in one embodiment is directed through a number offilters in series. In one embodiment, the first set of filters comprisesa number of bag filters to remove metals in the supernatant. The bagfilters can be staged in successive filtration capacity, e.g., the firstbag is for removing metal residuals larger than 50 microns, the secondbag for residual particulates over 15 microns, the third bag for 0.5microns or larger, etc. After the bag filters, the supernatant is routedthrough a plurality of ultra-filters, then lastly through membranes ornano-filters to further remove metals from the supernatant for aneffluent stream containing less than 1000 ppm metals in one embodimentand less than 500 ppm metals in another embodiment. The number of stagesand the filter sizes employed herein are representative, simply showingsuccessive reduction in filter sizes as metals are removed and recoveredfrom the supernatant. Actual sizing and the number of stages depends onthe size and amount of the metal residuals in the supernatant as well assubsequent effluent streams.

In one embodiment, reverse osmosis (RO) is used for reducing the metalcontents to a sufficiently low level for direct discharge to the sewer.The semi-permeable membranes for use in the RO can be made of knownmaterials, e.g., cellulose, cellulose acetate, polyamides andpolysulfone. In one embodiment, carbon nanotubes can be employed for theremoval of metals such as nickel compounds. The maximum pressure atwhich the supernatant (after a series of filtration) is fed through thefeed zone is determined by the strength of the membrane in the RO. Thepressure is at least 50 psi in one embodiment, at least 75 psi in asecond embodiment, and at least 100 psi in a third.

Formation of Secondary Catalyst Precursor: In one embodiment, at least aprecipitant is added to the mixture of supernatant and catalystprecursor gel in solution to change the solubility of the metalresiduals in the supernatant, forming another batch of catalystprecursor, e.g., secondary catalyst precursor. The precipitant can beadded batch-wise or continuously to the same equipment used in preparingthe catalyst precursor (“one-pot process”), or in a separate equipment.In one embodiment, the precipitant is added in an amount instoichiometric excess of that is required to react with select metalresidual(s) in the supernatant to form additional catalyst precursor. Inone embodiment, the ratio of precipitant to metal ions in the metalresidual(s) is at least 1.1:1 to 1.5:1. In a second embodiment, theratio ranges from 1.5:1 to 20:1. In a third embodiment, from 2:1 to10:1.

In one embodiment, the precipitant is added immediately after the visualappearance of any initial catalyst precursor, e.g., the appearance ofhaze forming. In another embodiment, the precipitant is added at least15 minutes after the completion of the co-precipitation reaction formingcatalyst precursor gel, wherein haze no longer forms, signifying thecompletion of the co-precipitation reaction. The precipitant changes thesolubility of the mixture solution containing the metal residuals toform at least a secondary catalyst precursor. The secondary catalystprecursor can be isolated and recovered along with the initial batch ofcatalyst precursor.

In one embodiment, the precipitant for use in generating the secondarycatalyst precursor is selected from the group of alumina, titanates,silicates and mixtures thereof. In another embodiment, the precipitantis selected from compounds of metals exhibiting amphoteric behavior.Examples of metals exhibiting amphoteric behavior include but are notlimited to Ni, Zn, Al, Sn, and Nb. In one embodiment, the precipitant isselected from the group of aluminium salts and a silicate. In anotherembodiment, the precipitant is selected from aluminium nitrate,aluminium sulphate, zinc nitrate, ammonium aluminate, ammonium zincate,niobium pentoxide, zirconium oxide, and mixtures thereof. In anotherembodiment, a sulphate is added to precipitate out metals in thesupernatant.

In one embodiment before the addition of precipitant, the pH of thesupernatant and catalyst precursor mixture is first adjusted to apre-select pH to facilitate the formation of a secondary catalystprecursor. The adjustment can be made with the addition of a basic oracidic chemical agent, e.g., an acid or a base such as ammoniumhydroxide. In one embodiment, the pH of the mixture is adjusted to alevel between 5 and 9. In another embodiment, the pH is adjust to about7. In one embodiment, the adjustment of the pH at a pre-selected pH isfor a sufficient amount of time and at a temperature such that at leasta portion of the metals in the supernatant precipitate before theaddition of the precipitant.

In one embodiment, the addition of the precipitant is carried out at atemperature ranging from ambient to about 80° C. and accompanied bymixing. In another embodiment, from 50-60° C. In one embodiment, afterthe addition of the precipitant causing the precipitation of a portionof the unreacted metal residuals, the mixture is left for the settlingof the catalyst precursors for 2-8 hours. In one embodiment after theaddition of the precipitant, the pH of the mixture is again adjusted toa pre-select pH to facilitate the subsequent isolation of the catalystprecursor(s). In one embodiment, the pH is optionally adjusted with theaddition of ammonia for a pH of less than 3. In another embodiment,nitric acid is added to bring the pH to about 5 to 6.5, for the in-situformation of secondary catalyst precursors such as aluminum molybdate,aluminum tungstate, and the like.

The solids containing the catalyst precursor (plus any secondary oradditional catalyst precursor) can be isolated using separation meansknown in the art, and the supernatant is collected. In one embodiment,the supernatant contains less than 5000 ppm each of the Group VIB metalsand the Promoter metals. In a second embodiment, less than 2000 ppm. Inone embodiment, the supernatant is sent to waste disposal directly as aneffluent stream. In yet another embodiment, the supernatant undergoesfurther treatment via any of the previously discussed recoverytechniques, e.g., chemical precipitation treatment and the like, toreduce metal levels in the effluent to less than 50 ppm.

Evaporative Process: In one embodiment, an evaporation step is employedseparately or preferably, in combination of another recovery step, e.g.,chemical precipitation, electro-coagulation, ion exchange, etc., torecover metals in the supernatant. In one embodiment evaporation isemployed after an acidic precipitation step, wherein an acid such asnitric acid is added to the supernatant to precipitate out at least someof the metal ions in the metal residuals as nitrates. As nitratestypically decompose at a temperature less than 500° C., the slurrycontaining mixed nitrates can be concentrated and evaporated to dryness.The temperature of the mixture is raised to between 200 and 500° C. inone embodiment, and between 400-450° C. in another embodiment. At thishigher temperature, nitrates are decomposed to their oxides, resultingin an admixture of respective metal oxides for further treatment, e.g.,with the addition of NH₄OH for subsequent use as a metal precursor feed.

Any of the metal recovery methods described above can used independentlyor in combinations thereof. Recovered metals can be recycled for use aspart of the metal precursor feed to the co-precipitation step for makingthe catalyst precursor, or incorporated into the catalyst precursor asdiluents. The choice of recovery technology depends on the type andconcentration of metal precursor feed employed in the making of thecatalyst, the waste water treatment capacity at the facility, amongstother factors.

In one embodiment, the recovery of the metal components can be carriedout via ion exchange technology using anion resins, cation resins,cation chelated resins, or combinations. In a second embodiment, therecovery is primarily via electro-coagulation. In a third embodiment,the recovery process employs a combination of ion-exchange andelectro-coagulation. In a fourth embodiment, chemical precipitation isused by itself. In a fifth embodiment, chemical precipitation is used incombination of any of the above recovery techniques for maximumrecovery, recovering a portion of metals in the supernatant prior totreatment by other techniques, or for recovering a portion of residualmetals in effluent streams from any of the other techniques. In a sixembodiment, the metals are recovered as secondary catalyst precursor(s).In a seventh embodiment, the recovery is via chemical precipitation incombination with using cation chelated resins for ion exchange recovery.

In one embodiment, recovered metals account for at least 10% of theGroup VIB metal precursor feed to the process. In another embodiment,recovered metals make up at least 20% of the incoming Group VIB metalprecursor feed. In a third embodiment, at least 30% of the metalprecursor feeds are recovered materials. In a fifth embodiment, lessthan 40% of the Promoter metal precursor feed for use in making thecatalyst precursor is from recovered metals.

After isolation and recovery of the catalyst precursor (and secondarycatalyst precursor if formed), it can be dried to remove water. Binders(or diluents), pore forming agents, shaping aid agents, etc.(collectively called “binders”) as known in the art can be incorporatedinto the catalyst precursor before being optionally shaped into variousshapes depending on the intended commercial use. The binder can be anorganic binder of the cellulose ether type and/or derivatives,polyakylene glycol such as polyethylene glycol (PEG), saturated orunsaturated fatty acid or a salt thereof, a polysaccharide derived acidor a salt thereof, graphite, starch, alkali stearate, ammonium stearate,stearic acid, mineral oils, and combinations thereof. Other materialsinclude rework material can also be added along with the peptizingagents, diluents, pore forming agents, etc. It should be noted that thebinder(s) can be added to the catalyst precursor, or they can be addedto the reaction mixture containing the metal precursors feed insolution, suspension or a combination thereof, in the process of formingthe catalyst precursor.

In one embodiment, the catalyst precursor is thermally treated or driedat a temperature between 50° C. to 200° C. in one embodiment, and at300° C. in another embodiment. In another embodiment, it is calcined ata temperature of at least 325° C. forming an oxide. In the final step,the catalyst precursor is sulfided forming the bulk catalyst. Thesulfiding agent can be any of elemental sulfur by itself; asulfur-containing compound which under prevailing conditions isdecomposable into hydrogen sulphide; H₂S by itself or H₂S in any inertor reducing environment, e.g., H₂. In one embodiment, hydrocarbonfeedstock is used as a sulfur source for performing the sulfidation ofthe catalyst precursor. Sulfidation of the catalyst precursor can beperformed in one or more reactors during hydroprocessing.

Further details regarding the binders, the thermal treatment, and thesulfidation of the catalyst precursor are described in a number ofpatent applications and patents, including U.S. Pat. Nos. 7,544,285,7,615,196, 6,635,599, 6,635,599, 6,652,738, 7,229,548, 7,288,182,6,566,296, 6,860,987, 6,156,695, 6,162,350, 6,299,760, 6,620,313,6,758,963, 6,783,663, 7,232,515, 7,179,366, 6,274,530; US PatentPublication Nos. US20090112011A1, US20090112010A1, US20090111686A1,US20090111685A1, US20090111683A1, US20090111682A1, US20090107889A1,US20090107886A1, US20090107883A1, US2007090024; U.S. patent applicationSer. No. 12/432,719, U.S. patent application Ser. No. 12/432,721, U.S.patent application Ser. No. 12/432,723, U.S. patent application Ser. No.12/432,727, U.S. patent application Ser. No. 12/432,728, and U.S. patentapplication Ser. No. 12/432,728, the relevant disclosures are includedherein by reference.

Reference will be made to the figures with block diagrams schematicallyillustrating different embodiments of a process for making amulti-metallic catalyst with minimal waste/metals in the effluentstream.

In FIG. 1, the first step 10 is a cogellation step, which involvesreacting metal precursors feed 11, e.g., promoter metal precursor feedand the Group VIB metal precursor feed to obtain a gel (or “cogel”). Inthe next step 20, at least 50 wt. % of the liquid (supernatant) isremoved from the catalyst precursor gel (suspension) via separationprocesses known in the art, e.g., filtering, decanting, centrifuging,etc., for a catalyst precursor in the form of a wet filter cake havingapproximately 5 to 50 wt. % liquid, being generally free of water orother solvent such as methanol and the like. The supernatant 13 containsfine particles (e.g., 0.1 to 10 microns) and colloidal particles (e.g.,0.001 to 1 micron) with up to 60% of the metal precursor reagentssupplied as feed to step 10 (the cogelation step). In one embodiment,supernatant 13 contains 0.1% wt. to 0.2% wt Ni, 0.2% wt to 0.8% wt Moand 0.05% wt to 0.4% wt W

In the optional chelating step 25, the catalyst precursor precipitate istreated with at least a ligating agent L, which can be the same ordifferent from any ligating agent that may have been used/incorporatedinto the metal precursor feeds (reagents) in the precipitating step.Chelating can be carried out by passing organic ligating agents/solventvapor through the filter cake, or that the filter cake can be washed ina solution containing the ligating agent. After the post precipitatechelating step, the drying step 26 can be any thermal drying techniqueknown in the art, e.g., flash drying, belt drying, oven drying, freezedrying, fluidized bed drying, etc. In one embodiment, the drying of thecatalyst precursor is performed at about 50 to 120° C. until a constantweight of the catalyst precursor is reached. In another embodiment, thedrying is done at a temperature between 50° C. to 200° C. for a periodranging from ½ hour to 6 hours.

In step 30, catalyst precursors are mixed together with water and otheroptional materials 32, e.g., peptizing agents, pore forming agents,diluent materials 13, and/or rework material. Rework material can be inthe form of filter cake material, extrudable dough and/or dryparticles/pieces of precursor materials from previous runs. The mixingtime depends on the type and efficiency of the mixing technique, e.g.,milling, kneading, slurry mixing, dry/wet mixing, or combinationsthereof and the mixing apparatus used, e.g., a pug mill, a blender, adouble-arm kneading mixer, a rotor stator mixer, or a mix muller.

In step 40, a shaping aid agent (binder or diluent) is added to themixture in a ratio of between 100:1 and 10:1 (wt. % catalyst precursorto wt. % shaping aid). Diluents can be the same as or different from anydiluents that may have been previously added. Shaping step 40 can bedone via any of extrusion, pressing, pelletizing, and the like.

After shaping, the catalyst precursor undergoes optional thermaltreatment (calcining) in step 50, if desired. The thermal treatment canbe at about 300° C. to 750° C. in a suitable atmosphere, e.g., inertssuch as nitrogen or argon, or steam. In the calcination process, thecatalyst precursor gets converted into an oxide precursor. In thesulfiding step 60, the catalyst precursor is converted into a bulkmulti-metallic catalyst. Although not shown, the catalyst precursor canalso be sulfided in-situ, e.g., in the same reactors duringhydroprocessing.

FIG. 2 illustrates another embodiment wherein additional catalystprecursor is formed in addition to the previously formed catalystprecursor. In the figure, unreacted metal residuals are “recovered” byforming additional, or a secondary catalyst precursor (step 15). In thisembodiment, after the formation of the catalyst precursor in step 10, atleast a precipitant 9 is added to the catalyst precursor gel/supernatantmixture 21. An acid or base 11 is added to adjust the pH so that therecovered metals form a secondary precursor. The additional catalystprecursor is incorporated into the catalyst precursor previously formed(in the co-precipitation step) for recovery and further processed toform a bulk multimetallic catalyst.

FIGS. 3-8 schematically illustrating various embodiments of the processblock 70 in FIG. 1 to recover metals from the supernatant 13. In FIGS.3-4, electro-coagulation technology is employed to recover at least 90%recovery of metal residuals from the supernatant 13. In one embodiment,recovered Group VIB metals in their anionic form are sent to thecogelation step 10 as metal precursor feed. In another embodiment, someof the Promoter metals are also recovered as ionic compounds forsubsequent reuse in the cogelation step.

In FIG. 3, the supernatant 13 is first sent to electro-coagulation step71. Promoter metal residuals in the supernatant 13, e.g., group VIIIcompounds, come into contact and react via oxidation/reduction with thedissolved metallic ions form in-soluble by-products such as NiAlO₄. Theinsoluble by-product Promoter metal salts 712 are removed from solution,yielding effluent stream 711 substantially free of Promoter metals(e.g., with less than 100 ppm metals). Chemical precipitation step 72 isnext employed to recover/remove at least 75% of the Group VIB metalsfrom effluent stream 711 with the addition of an acid. The pH isadjusted to cause selective precipitation of at least 75% of the GroupVIB metals in the effluent stream. In one embodiment, the pH is reducedto less than 3.5 to precipitate more than 75% of the Mo and/or W solublecomplexes.

After the acid precipitation step 72, the solid precipitate containingGroup VIB metal complexes is separated from solution in separation zone73 by known separation means. A basic solution, e.g., concentratedammonium hydroxide solution is added to dissolve the solid metal oxideprecipitate in step 76, producing a saturated solution having a pH ofabout 5 to about 7. The solution may be cooled from its saturationtemperature to room temperature wherein ammonium polymolybdate (e.g.,ammonium heptamolybdate) and ammonium polytungstate (e.g., ammoniumheptatungstate) precipitate out. In one embodiment, the solution isrouted to the cogelation step 10 as metal precursor feed.

Remaining metal (less than 25% of incoming metals in one embodiment, andless than 5% in a second embodiment) is further removed in chemicalprecipitation step 74. Filtrate solution 731 is treated in precipitationzone 74 with an alkaline earth metal compound, e.g., calciumion-containing solution containing for example from about 0.1 to 80 wt.% calcium chloride, to selectively precipitate out the Group VIB metals,e.g., molybdenum, tungsten, etc., as calcium molybdate (CaMoO₄), calciumtungstate (CaWO₄), etc. The slurry is passed on to separation zone 75for isolation and recovery of CaMoO₄, CaWO₄, etc. for disposal, andeffluent 81 for waste water treatment or sewer. The effluent 81 may befurther reduced with carbon monoxide or low molecular weight oxygenatedhydrocarbons, resulting in the precipitation of a hydrated chromiumoxide product and a spent liquor containing alkali metal salts ofcarbonate or bicarbonate, which is dehydrated to yield alkali metalsalts and waste water to sewer.

FIG. 4 illustrates another variation of electro-coagulation metalrecovery, wherein the supernatant 13 first undergoes chemicalprecipitation. In the precipitation step 72 at a pre-selected pH, atleast 75% of the Group VIB metals initially present are removed. Slurrycontaining Group VIB metal complexes goes to separation zone 73, whereeffluent 731 contains less than 25% of the incoming Group VIB metals isrecovered and sent to an electro-coagulation step 71. In this step,electrodes form insoluble complexes with the various Promoter metals inthe effluent solution 731, removing at least 75% of Promoter metals asinsoluble complexes such as NiAlO₄ for waste disposal. The filtrate 711containing very low levels of metals (either Group VIB metals orPromoter metals) is optionally treated in basic precipitation step 74with a solution containing alkaline-earth metals, for example, forming aslurry. From separation zone 75, precipitate containing CaMoO₄ and CaWO₄is sent to waste disposal, and the effluent or filtrate 81 containingless than 10 ppm of each of the Group VIB and Promoter metals can besent to waste water treatment/sewer.

FIGS. 5-8 illustrate the use of ion-exchange technology to recover atleast 90% of the metals in the supernatant. The metal recovery ratedepends on a number of factors, including but not limited to the typesof resins used in the ion-exchange bed, the concentration of the metalsin the supernatant, the pH of the supernatant, as well as the flowvelocity of the supernatant 13 through the ion-exchange resin.

In FIG. 5, cationic exchanger 77 is used first to extract Promotermetals, e.g., group VIII, group IIB metals such as nickel from thesupernatant stream 13. In this step, a resin selectively absorbsPromoter metals such as nickel, cobalt, and the like from an incominglevel of >1000 ppm to less than 50 ppm in the effluent stream 771. Theeffluent stream 771 undergoes chemical precipitation treatment step 72to recover most of the Group VIB metals as oxides. The solid precipitateis separate from solution in separation zone 73. NH₄OH is added in step76 to dissolve Group VIB metal complexes for use in cogelation step 10as metal precursor feedstock ammonium polymolybdate (e.g., ammoniumheptamolybdate or AHM) and ammonium polytungstate (e.g., ammoniumheptatungstate or AHT). From separation zone 73, the effluent 731 istreated with a solution containing alkaline earth metal ions, e.g.,lime, in precipitator 74 to selectively precipitate out Group VIBmetals, e.g., molybdenum, tungsten, etc., forming a slurry. Fromseparation zone 75, filtrate 81 is recovered and sent to waste treatmentor sewer as an effluent stream. Precipitate containing calciummolybdate/calcium tungstate can be sent to waste disposal.

FIG. 6 illustrates another embodiment of metal recovery viaion-exchange. The supernatant 13 first undergoes chemical precipitation72 at a pre-selected pH, forming a slurry containing metal complexes. Inseparation step 73, the metal complexes are isolated and recovered. Instep 76 with further treatment with a basic solution, e.g., concentratedammonium hydroxide solution, at least 75 mole % of the Group VIB metalsinitially present in the supernatant are recovered for re-use as AHMand/or AHT metal precursor feeds.

From separation zone 73, the filtrate containing less than 25% of theGroup VIB metals enters cation-exchange column 77, wherein at least 90%of Promoter metals such as nickel is recovered and sent to thecogelation step 10. The effluent 771 from the cation-exchange column canbe sent to waste treatment, or as shown, treated in precipitator 74 witha solution containing alkaline-earth metal ions such as lime, formingprecipitates which can be isolated and recovered in step 75 forsubsequent waste disposal.

In FIG. 7, instead of or in addition to the chemical precipitation step72 (as shown in FIG. 6), anion solvent extraction or anion-exchangecolumn 77B is employed to selectively remove molybdate and tungstateanions from the effluent stream 771. In (optional) pH treatment zone 78,the effluent stream 771 is first neutralized to a pH of 3 to 6.5 by theaddition of a suitable base, such as sodium hydroxide, prior to enteringthe anion-exchange column 77B. After loading with Group VIB metalcomplexes such as molybdate anions/tungstate anions, the resin inconveniently eluted in step 76 with an aqueous solution of ammoniumhydroxide. The resultant eluate containing ammonium polymolybdate and/orammonium polytungstate is recycled back to step 10 in FIG. 1 for thecogelation reaction.

The effluent stream from the anion-exchange column 77B in one embodimentis treated with a solution containing alkaline earth metal ions, e.g.,lime, in precipitation zone 74 to selectively precipitate out anyremaining Group VIB metals, e.g., molybdenum, tungsten, etc., whichcompounds are subsequently separated out in separation zone 75, for theeffluent to go to waste treatment or sewer. The precipitate containingcalcium molybdate/calcium tungstate can be sent to waste disposal.

As illustrated in FIG. 7, the cation-exchange step 77A precedes theanion-exchange step 77B. However, in another embodiment of ion-exchangetechnology (not shown) and depending on the pH of the stream to betreated, anion-exchange 77B can be first carried out to recover/removeGroup VIB metal complexes from the supernatant 13 as a solutioncontaining ammonium polymolybdate and/or ammonium polytungstate. Theeffluent stream from the anion-exchange column is next routed to acation-exchange zone 77, wherein the pregnant solution (eluate)containing Promoter metal salts such as Ni(NO₃)₂ is recovered andre-used in the cogelation step 10. The effluent stream from thecation-exchange zone 77A can be optionally further treated with achemical precipitation process, whether with an alkaline-earth metalsolution (as in step 74) or with an acid (as in step 72), depending onthe concentration and metal components contained as well as thecapability of the waste water treatment facility.

FIG. 8 illustrates the use of ion-exchange technology in combinationwith electro-coagulation to recover unreacted metal residuals from thesupernatant stream 13. The supernatant stream 13 first undergoeschemical precipitation step 72 prior to ion-exchangetreatment/electro-coagulation to remove the residual metal components.In acid precipitator 72, the supernatant stream 13 is adjusted to apre-selected pH to precipitate out at least 75% of the Group VIB metalsas oxides. After the separation step 73, the metal complexes are furthertreated in step 76 with a basic solution, e.g., concentrated ammoniumhydroxide solution, to dissolve solid metal precipitate. Group VIBcomplexes such as chromates, molybdates, and the like are recovered andrecycled back for use as metal precursor feed for the cogelation step10.

From the separation zone 73, the filtrate containing essentially all ofthe incoming Promoter metals and less than 25% of the incoming Group VIBmetals is sent to a cation exchange column 77A. In the cation-exchanger77A, a resin is selected to selectively absorb Promoter metals such asnickel, cobalt, and the like from an incoming level of >1000 ppm to lessthan 50 ppm in the effluent stream 771.

After the cation-exchange step 77A, the effluent stream 771 can be sentdirectly to the precipitator 74 to remove most of the Group VIB metalsas calcium molybdate, calcium tungstate, and the like for wastedisposal. In one embodiment, the effluent stream 771 undergoes furthertreatment either in an anion-exchanger column 77B, anelectro-coagulation vessel 71, or in both process steps configured inseries to maximize the removal and recovery of metals in the effluentstream.

In another embodiment, before chemical treatment with an alkaline earthmetal solution in precipitator 74, the effluent stream exitinganion-exchange zone 77 can be further treated in anion-exchange column77B, electro-coagulation vessel 71, split into two separate streams fortreatment in both (as illustrated). In another embodiment (not shown),the effluent stream can be treated in the anion-exchange column 77B andfollowed by metal recovery in the electro-coagulation vessel 71. If thetreatment is via anion-exchange 77B, the cationic resin can besubsequently eluted (not shown) with an aqueous solution of ammoniumhydroxide. The resultant eluate containing ammonium polymolybdate and/orammonium polytungstate is recycled back to the cogelation step as metalprecursor feed.

In one embodiment, with an additional metal recovery step viaelectro-coagulation vessel 74 and with the use of aluminium as thecathodes, aluminium forms insoluble complexes with the various Group VIBmetals in the effluent stream 771, forming metal complexes such asAl₂(MoO₄)₃, Al₂(WO₄)₃, etc., which can be recovered/reused in thecogelation step 10 as metal precursor feed.

In yet another embodiment (not shown), metal removal can be carried outvia ion-exchange (cationic and/or anionic exchange) in combination withelectro-coagulation and chemical precipitation, either via adjustment toa pre-selected pH with the addition of an acidic or basic solution,e.g., a solution containing alkali-earth metal ions.

Use of the Catalyst Employing Recycled/Recovered Metals: Amulti-metallic catalyst prepared with recycled/recovered metals can beused in virtually all hydroprocessing processes to treat a plurality offeeds under wide-ranging reaction conditions. The catalyst withrecycled/recovered metals also shows excellent catalytic activity,giving over 90% HDN (hydrodenitrogenation) conversion rate in thehydrotreating of heavy oil feedstock such as VGO.

It should be appreciated that the methods to recover/recycle metalcomponents for use as metal precursor feed as illustrated above can bevaried without departing from the essential characteristics of theinvention. For example, different recovery technologies can be usedindividually or in combination, e.g., chemical precipitation,ion-exchange, or electro-coagulation. The selection and/or ordering ofthe specific recovery technology to employ depends on the concentrationand composition of the supernatant with metal components to berecovered, and the waste material handling capability of the facility.

EXAMPLES

The following examples are intended to be non-limiting. In the examples,metal levels were analyzed using inductively coupled plasma (ICP).

Comparative Example

A catalyst precursor of the formula (NH₄) {[Ni_(2.6)(OH)_(2.08)(C₄H₂O₄²⁻)_(0.06)] (Mo_(0.35)W_(0.65)O₄)₂}, along the line of Example 1, USPatent Publication No. US 2009-0112010A1 was prepared was prepared asfollows: 52.96 g of ammonium heptamolybdate (NH₄)₆Mo₇O₂₄.4H₂O wasdissolved in 2.4 L of deionized water at room temperature. 73.98 g ofammonium metatungstate powder was then added to the above solution andstirred at room temperature until completely dissolved. 90 ml ofconcentrated (NH₄)OH was added to the solution with constant stirring. Asecond solution was prepared containing 174.65 g of Ni(NO₃)₂.6H₂Odissolved in 150 ml of deionized water and heated to 90° C. The hotnickel solution was slowly added over 1 hr to the molybdate/tungstatesolution. The resulting mixture was heated to 91° C. and stirringcontinued for 30 minutes. The precipitate was dispersed into a solutionof 10.54 g of maleic acid dissolved in 1.8 L of deionized (DI) water andheated to 70° C. The resulting slurry was stirred for 30 minutes at 70°C. and filtered.

The supernatant from the filtration step contained 7200 ppm Mo, 3600 ppmW, and 1450 ppm Ni. The supernatant would have to undergo expensivewaste treatment to comply with environmental regulations for plantdischarge water.

Example 1

800 g of water was added into a heated 2 L round-bottom (RB) flask,equipped with a condenser, overhead stirrer, TC and a pH probe. 17.69 gof Ammonium heptamolybdate tetrahydrate (AHM) was added to the flask,and stirred till completely dissolved for a pH=5.16@18.9° C. 24.68 g ofammonium metatungstate (AMT) was next added, and mixture was stirreduntil completely dissolved for a pH of 5.13 at 18.9° C. The pH of themixture was adjusted with ammonium hydroxide for a pH of 9.6 at 23.7° C.The mixture was heated, and the mixture pH was measured at 7.66 at 81.6°C. Separately, 58.24 g nickel nitrate hexahydrate was dissolved in 50 gof water. The nickel solution was added to the hot mixture in theprevious step with vigorous stirring over 20 minutes, for a mixturehaving a pH of 6.17 at 79.6° C. In the next step, 2.03 g of maleic acidwas added to the mixture for a pH of 5.98 at 79° C. The pH of themixture was adjusted to 7.07 at 81.4° C. with concentrated ammoniumhydroxide. The mixture was stirred continuously for 80 minutes. Catalystprecursor was formed as a gel in solution.

In the subsequent steps, more (secondary) catalyst precursor was formedwith the addition of 40 g of aluminum nitrate to the catalyst precursorgel mixture and stirred for 1 hour. The pH was then adjusted 5.3 (at 80°C.) with 2.9 g of concentrated HNO₃. The mixture was stirred for 1 hourfor a final pH of 5.39 at 80° C. The hot slurry was filtered forrecovery of 816 g of filtrate and filter cake, which was subsequentlydried in air. The solids were dried at 120° C. over-night in air, for˜80 g of solids. An analysis of the filtrate gave 850 ppm of Mo, 46 ppmof W and 652 ppm of Ni, for 97% metal recovery.

The filtrate was treated with an excess of hydrated slurry of CaO inwater at about 80° C., forming a precipitate. Solid liquid separationwas carried out to isolate the precipitate, giving an effluent with lessthan 20 ppm Mo and W and less than 10 ppm Ni.

Example 2

Chemical Precipitation followed by Electro coagulation (EC): Example 1was repeated. After the catalyst precursor was isolated and recovered,the supernatant was collected and analyzed showing 7149 ppm Mo, 3591 ppmW and 1433 ppm Ni. The pH of the supernatant was adjusted to 3.0 withconcentrated nitric acid. About 342 g of the supernatant were placedinto 500 ml EC cell equipped with 2 rectangular aluminum electrodes.Voltage of 6 V was applied to the electrodes to keep a DC current of 5Ampere flowing through the cell for 15 minutes. The resulting slurry hadpH of 5.6 at 78° C. The slurry was filtered and cooled to roomtemperature, giving a first filtrate containing about 86 ppm of Mo, lessthan 6 ppm of W and 117 ppm of Ni. The pH of the filtrate was adjustedto 7.5 with 1M NaOH. It was then treated in the EC cell under the sameconditions as in the first EC step. The resulting slurry had pH of 6.8at 79° C. Solid liquid separation was carried out forming a secondfiltrate which contained about 22 ppm of Mo, less than 6 ppm of W andabout 5.2 ppm of Ni.

Example 3

Example 1 was repeated. After the catalyst precursor was isolated andrecovered, the supernatant was collected and analyzed showing 7149 ppmMo, 3591 ppm W and 1433 ppm Ni. The pH of the supernatant was 7.8 at 20°C. 385 g of the supernatant were placed into 500 ml EC cell equippedwith 2 rectangular aluminum electrodes. Voltage of 4V was applied to theelectrodes to keep a DC current of 5 A flowing through the cell for 15minutes. The resulting slurry had pH of 7.3 at 72° C. The slurry wasfiltered and cooled to room temperature giving a first filtrate,containing 6733 ppm of Mo, 986 ppm of W and 20 ppm of Ni. The firstfiltrate was placed into a 500 ml flask equipped with overhead stirring,then its pH was adjusted to 1.4 with concentrated nitric acid. A whiteprecipitate immediately formed as the result of the acid adjustment. Thestirring was kept for 20 min and then stopped. The mixture was allowedto settle for 2 hours. Solid liquid was carried out giving a secondfiltrate, containing 1286 ppm of Mo, 236 ppm of W and 20 ppm of Ni. Thesecond filtrate was treated with an excess of CaO slurry in water at 80°C. to neutralize the pH and reduce Mo and W levels to less than 20 ppm,and Ni below 10 ppm.

Example 4

Example 1 was repeated. After the catalyst precursor was isolated andrecovered, the supernatant was collected and analyzed showing 7149 ppmMo, 3591 ppm W and 1433 ppm Ni. The pH of the supernatant was 7.8 at 20°C. About 1 L of the supernatant was placed into 2 L flask equipped withoverhead stirrer. The pH of the supernatant was adjusted to 1.2 withconcentrated nitric acid. A white precipitate immediately formed as theresult of the acid adjustment. The stirring was continued for 20 min andthen stopped. The mixture was cooled in an ice bath to 10° C. andallowed to settle for 2 hours. The mixture was filtered, giving 396 g offirst filtrate. A sample of the first filtrate was taken for the metalanalysis by ICP, showing 901 ppm of Mo, 208 ppm of W and 1511 ppm of Ni.The pH of the first filtrate was adjusted to 7.5 with 1M NaOH. It wastransferred to the EC cell as described in the Example 3, and treatedfor 15 min under the cell DC current of 5 Ampere at 6 V, giving a slurrywith pH of 6.7 at 81° C. The slurry was filtered, giving a secondfiltrate, which contained 115 ppm of Mo, 20 ppm of W and 2 ppm of Ni.The second filtrate was treated with an excess of CaO slurry in water at80° C. to reduce Mo and W levels below 20 ppm.

Example 5

Example 1 was repeated. After the catalyst precursor was isolated andrecovered giving a supernatant. After recovery, the supernatant wasanalyzed, showing 3782 ppm Mo, 750 ppm W and 1868 ppm Ni. The pH was 7.8at 20° C. 1 L of the filtrate supernatant was placed into 2 L flaskequipped with overhead stirrer. The pH of the filtrate was adjusted to1.2 with concentrated nitric acid. A white precipitate immediatelyformed as the result of the acid adjustment. The stirring was continuedfor 20 min. The mixture was cooled in an ice bath to 10° C. and allowedto settle for 2 hours. The mixture was filtered, giving a firstfiltrate. The first filtrate was analyzed showing to contain 901 ppm ofMo, 208 ppm of W and 1511 ppm of Ni.

200 ml of the first filtrate was contacted with 20 ml of Amberlite™ 748ion exchange resin in H+ form. The mixture was placed into a 500 mlbottle and shaken for 2 hours. The mixture was filtered, giving a secondfiltrate. The second filtrate was analyzed showing less <20 ppm of Moand W and 1426 ppm of Ni. The pH of the second filtrate was adjusted to6.5 with concentrated solution of ammonium hydroxide forming a slurry.200 ml of the slurry mixture was brought into contact with 20 ml ofAmberlite™ 748 ion exchange resin in NH₄+ form. The mixture was placedinto a 500 ml bottle and shaken for 2 hours. It was filtered as inprevious step to obtain resin-free liquid as a third filtrate. In ICPmetal analysis, the third filtrate shows less than 3 ppm Ni.

Mo and W were recovered by regenerating the resin with ammoniumhydroxide solution, followed by ion exchange with sulfuric acid toconvert the resin to H+ form. Ni was recovered by washing the resin witha solution of sulfuric acid, followed by ion exchange with ammoniumhydroxide to obtain ammonium form of the resin. It should be noted herethat due to its weak acid nature, the resin acts as an anion exchangeresin in a acidic pH range below its point of zero charge, and as acation exchange resin above the point of zero charge at a neutral tobasic pH.

Example 6

In this example, the effluent was acid treated, followed by a cationexchange and/or lime treatment. Example 1 was repeated and supernatantfrom the catalyst precursor isolation step was collected and analyzed,showing 3782 ppm Mo, 750 ppm W and 1868 ppm Ni. The pH of thesupernatant was 7.8 at 20° C. 1 L of the filtrate was placed into 2 Lflask equipped with overhead stirrer. The pH of the supernatant wasadjusted to 1.2 with concentrated nitric acid. A white precipitateimmediately formed as the result of the acid adjustment. The stirringwas continued for 20 min. The mixture was cooled in an ice bath to 10°C. and allowed to settle for 2 hours. The mixture was filtered, giving afirst filtrate. A sample of the first filtrate was taken for the metalanalysis by ICP. It contained 901 ppm of Mo, 208 ppm of W and 1511 ppmof Ni. 200 ml of the first filtrate was contacted with 40 ml of DowexG-26H ion exchange resin in H+ form. The mixture was placed into a 500ml polypropylene bottle and shaken for 2 hours. The slurry was filtered,giving a second filtrate which was analyzed, showing 890 ppm Mo, 201 ppmW and 573 ppm Ni.

The second filtrate was treated with an excess of CaO slurry in water at80 C to reduce Mo and W levels below 20 ppm and Ni below 10 ppm. Theresin was regenerated with an acid according to manufacturer's suggestedprocedures and re-used. It should be noted that lime treatment may notbe necessary if metal recovery is deemed sufficient after acidprecipitation.

For the purposes of this specification and appended claims, unlessotherwise indicated, all numbers expressing quantities, percentages orproportions, and other numerical values used in the specification andclaims, are to be understood as being modified in all instances by theterm “about.” Accordingly, unless indicated to the contrary, thenumerical parameters set forth in the following specification andattached claims are approximations that can vary depending upon thedesired properties sought to be obtained by the present invention. It isnoted that, as used in this specification and the appended claims, thesingular forms “a,” “an,” and “the,” include plural references unlessexpressly and unequivocally limited to one referent. As used herein, theterm “include” and its grammatical variants are intended to benon-limiting, such that recitation of items in a list is not to theexclusion of other like items that can be substituted or added to thelisted items.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to make and use the invention. The patentable scope is defined bythe claims, and can include other examples that occur to those skilledin the art. Such other examples are intended to be within the scope ofthe claims if they have structural elements that do not differ from theliteral language of the claims, or if they include equivalent structuralelements with insubstantial differences from the literal languages ofthe claims. All citations referred herein are expressly incorporatedherein by reference.

1. A process for forming a bulk hydroprocessing catalyst, the methodcomprises: co-precipitating at reaction conditions at least a Group VIBmetal precursor feed and at least a Promoter metal precursor feedselected from Group VIII, Group IIB, Group IIA, Group IVA andcombinations thereof, to form a product mixture comprising a firstcatalyst precursor and a first supernatant containing at least aPromoter metal residual and at least a Group VIB metal residual in anamount of at least 10 mole % of the metal precursor feeds; adding atleast a precipitant to the product mixture at a molar ratio ofprecipitant to metal residuals ranging from 1.5:1 to 20:1 to precipitateat least 50 mole % of metal ions in the residuals forming additionalcatalyst precursor; isolating the catalyst precursors from the productmixture, forming a second supernatant containing less than 5000 ppm ofmetal ions in the metal residuals; and sulfiding the catalyst precursorsforming the bulk catalyst.
 2. The process of claim 1, further comprisingdrying the first and additional catalyst precursors at a temperature of150 to 300° C. before the sulfidation step.
 3. The process of claim 2,wherein the drying is at a temperature of 200° C. or less.
 4. Theprocess of claim 1, further comprising calcining the first and secondcatalyst precursors at a temperature of at least 300° C. before thesulfidation step.
 5. The process of claim 4, wherein the calcination isat a temperature of at least 325° C. to form at least one catalystprecursor having the formula (X)_(b)(Mo)_(c)(W)_(d)O_(z); wherein X isNi or Co, the molar ratio of b:(c+d) is 0.5/1 to 3/1, the molar ratio ofc:d is >0.01/1, and z=[2b+6 (c+d)]/2.
 6. The process of claim 3, whereinthe drying is at a temperature of 200° C. or less, forming at least acatalyst precursor having the formula A_(v)[(M^(P))(OH)_(x)(L)^(n)_(y)]_(z) (M^(VIB)O₄), wherein A is at least one of an alkali metalcation, an ammonium, an organic ammonium and a phosphonium cation, M^(P)is selected from the group of Group VIII, Group IIB, Group IIA, GroupIVA and combinations thereof, P is oxidation state with M^(P) having anoxidation state of either +2 or +4 depending on the selection of M^(P),L is at least a ligating agent L having an charge n<=0; M^(VIB) is atleast a Group VIB metal having an oxidation state of +6, M^(P):M^(VIB)has an atomic ratio of 100:1 to 1:100; v−2+P*z−x*z+n*y*z=0; and0<y≦−P/n; 0<x≦P; 0<v≦2; 0<z.
 7. The process of claim 6, wherein M^(P) isat least a Group VIII metal.
 8. The process of claim 1, wherein theisolation of the first and additional catalyst precursors is via atleast one of filtering, decanting, centrifuging, and combinationsthereof.
 9. The process of claim 1, prior to the addition of theprecipitant, further comprising adjusting the pH of the mixture to apre-selected pH to facilitate the formation of the additional catalystprecursor.
 10. The process of claim 1, prior to the isolation of thefirst and additional catalyst precursors, further comprising adjustingthe pH of the mixture to a pre-selected pH to facilitate the isolationof the first and additional catalyst precursors.
 11. The process ofclaim 9, wherein the pH of the mixture is adjusted by adding at least anacid or a base.
 12. The process of claim 10, wherein the pH of themixture is adjusted by adding nitric acid.
 13. The process of claim 12,wherein the pH of the mixture is adjusted to about 5 to 6.5.
 14. Theprocess of claim 1, wherein the precipitant is selected from compoundsof metals exhibiting amphoteric behavior.
 15. The process of claim 14,wherein the precipitant is selected from compounds of Ni, Zn, Al, Sn,and Nb.
 16. The process of claim 15, wherein the precipitant is selectedfrom aluminium nitrate, aluminium sulphate, zinc nitrate, ammoniumaluminate, ammonium zincate, niobium pentoxide, zirconium oxide, andmixtures thereof.
 17. The process of claim 15, wherein the precipitantis ammonium aluminate.
 18. The process of claim 1, wherein theprecipitant is selected from the group of alumina, alumina silica,titanates, silicates and mixtures thereof.
 19. The process of claim 1,further comprising: supplying the second supernatant to a reactor vesselhaving a plurality of electrodes having a positive or a negative chargeprovided by a power supply, forming a slurry containing insoluble metalcompounds; recovering the insoluble metal compounds, forming a firsteffluent stream containing less than 100 ppm metals.
 20. The process ofclaim 1, further comprising: providing at least an exchange resin;contacting the second supernatant with the ion exchange resin for atleast 50% of metal ions in at least one of the metal residuals in thesecond supernatant to be bound onto the resin, forming an effluentstream containing less than 100 ppm metals.
 21. The process of claim 1,further comprising: treating the second supernatant with at least anadditive selected from the group of acids, sulfide-containing compound,bases, and mixtures thereof under mixing conditions for a sufficientamount of time to precipitate at a pre-selected pH at least a portion ofthe first and second metal residuals, forming an effluent streamcontaining less than 100 ppm metals.
 22. The process of claim 1, whereinthe sulfiding of the first and second catalyst precursors forming thebulk catalyst is either before or after loading the catalyst precursorsinto a hydroprocessing reactor.